The present disclosure relates to metal interconnect structures, and particularly to metal interconnect structures having etch-bias independent height and methods for manufacturing the same.
Reactive ion etch (RIE) can be used to produce trenches having depths that are dependent on the width of a trench. Simultaneous etching of multiple trenches having different widths result in formation of narrower trenches having a lesser depth and wider trenches having a greater depth. The variations in the depths of the trenches depending on the width of the trenches are referred to as a RIE lag.
The RIE lag causes non-uniformity in the depths of the trenches. The resulting metal lines obtained by filling the trenches with a conductive material have different depths that depend on the width of the metal lines. Narrower metal lines have a lesser height and wider metal lines have a greater height. As the minimum width of the metal lines shrinks with scaling of semiconductor devices, the effect of the RIE lag becomes severer. The variation in the height of metal lines as a function of width is a significant obstacle for device scaling.